Conductive conjugate fiber

ABSTRACT

A conjugated conductive fiber including a non-conductive layer and a conductive layer, in which: the non-conductive layer accounts for at least 70% of a surface of the fiber; the non-conductive layer is a polyester obtained by copolymerizing a metal sulfonate group-containing isophthalic acid and a polyalkylene glycol; and the conductive layer is a thermoplastic polymer containing titanium oxide particles each having a conductive coating film. The conjugated conductive fiber provides a polyester-based conjugated yarn high in antistatic performance and easy to handle, which can be dyed under normal pressure with improved color developing property after dying.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a conjugated conductive fiber in which the generation of static electricity is suppressed.

2. Description of the Related Art

Sweaters, fleeces, and the like, each of which are made of acrylic fibers, are not free of generation of static electricity when one takes off those clothes after wearing. In order to prevent the generation of static electricity, there has been a demand for conductive yarns which can be blended with the acrylic fibers.

In order to respond to this demand, blending of acrylic fibers provided with conductivity has been considered. Some approaches have been proposed heretofore (see JP-B-61-15167 and JP-A-9-31747).

However, production of an acrylic conductive yarn involves numerous problems. A method of producing the acrylic conductive yarn is, for example, a method involving adding conductive particles to an acrylic resin, e.g., such a complicated method as described below. The method involves: preparing a spinning dope by dissolving an acrylic polymer and conductive particles made of, for example, conductive titanium oxide in an organic solvent; ejecting the spinning dope to a coagulating solution; spinning the resultant by a semi-dry method; and removing the solvent by a post treatment. At the time of the removal of the solvent, voids occur in the acrylic fiber itself, which adversely affects the conductivity of the fiber.

In view of the foregoing, the use of a conductive yarn made of another material has been considered. However, when the conductive yarns made of the other material is blended with acrylic fibers, it becomes necessary to perform two processes involving dyeing the acrylic fiber and dyeing the other material.

SUMMARY OF THE INVENTION

A problem to be solved by the present invention is to provide a conjugated conductive fiber which involves few problems in being provided with conductivity and can be dyed under the same conditions as those for an acrylic fiber.

The present invention has solved the above-mentioned problem by constituting a conjugated conductive fiber as described below. The conjugated conductive fiber is a conjugated conductive fiber including a non-conductive layer and a conductive layer, in which: the non-conductive layer accounts for at least 70% of a surface of the fiber; the non-conductive layer is a polyester obtained by copolymerizing a metal sulfonate group-containing isophthalic acid and a polyalkylene glycol; and the conductive layer is a thermoplastic polymer containing titanium oxide particles each having a conductive coating film.

That is, the inventors of the present invention have intensively studied a conductive yarn. As a result, the inventors have focused on a conjugated conductive fiber obtained by melt spinning to obtain a conductive fiber which can be dyed under the same conditions as those for an acrylic fiber and involves few problems in production. Then, the inventors have achieved the present invention by using a polymer which can be dyed under the same conditions as those for an acrylic fiber, i.e., which can be subjected to cationic dyeing under normal pressure as a polymer in the non-conductive layer of the surface of the conjugated conductive fiber.

The conjugated conductive fiber of the present invention can be industrially produced with ease at a low cost, and can be dyed under normal pressure with good color developing property. Accordingly, when the conjugated conductive fiber is blended with an acrylic material, the fiber can suppress the generation of static electricity of a product, and can be dyed under the same conditions as those for an acrylic fiber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating the cross-section surface of the polyester-based conjugated conductive fiber in a first embodiment of the present invention.

FIG. 2 is a view illustrating the cross-section surface of the polyester-based conjugated conductive fiber in a second embodiment of the present invention.

FIG. 3 is a view illustrating the cross-section surface of the polyester-based conjugated conductive fiber in a third embodiment of the present invention.

FIG. 4 is a view illustrating the cross-section surface of the polyester-based conjugated conductive fiber in a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A non-conductive layer of a conjugated conductive fiber of the present invention is a polyester obtained by copolymerizing a metal sulfonate group-containing isophthalic acid and a polyalkylene glycol.

The content of the metal sulfonate group-containing isophthalic acid (hereinafter, referred to as “SIP”) is preferably 0.5 to 10 mol % with respect to an acid component contained in the polyester of the non-conductive layer. When the content of the SIP is less than 0.5 mol %, cationic dyeability decreases, and dyeing cannot be performed under the same conditions as those for an acrylic fiber. As a result, when the conjugated conductive fiber is blended with an acrylic fiber and then dyed, the conductive fiber tends to appear as spots. Further, when the content of the SIP exceeds 10 mol %, a degree of polymerization does not increase, and the molecular weight of the polymer does not increase. As a result, the polymer tend not to be formed into a fiber when spinning is performed.

The SIP is, for example, a dimethyl 5-metal sulfoisophthalate (hereinafter, referred to as “SIPM”) or a compound obtained by esterifying a dimethyl group of the SIMP with ethylene glycol (hereinafter, referred to as “SIPE”). When the SIPM is introduced into a slurry tank in a large amount, physical properties of the slurry may be deteriorated. Accordingly, the SIPE is preferably adopted.

Further, examples of the metal in the SIP include sodium, potassium, and lithium. Of those, sodium is most preferred.

Further, the content of a polyalkylene glycol is preferably 1.5 to 6 wt % with respect to the polyester of the non-conductive layer. When the content of the polyalkylene glycol is less than 1.5 wt %, dyeability under normal pressure deteriorates, and it becomes necessary to perform dyeing under high pressure. As a result, when the conjugated conductive fiber is blended with an acrylic fiber and then dyed under normal pressure under the same conditions as those for the acrylic fiber, a dyeing concentration of a conductive yarn is low, and the yarn tends to appear as spots. Further, when the content of the polyalkylene glycol exceeds 6 wt %, the degree of polymerization does not increase, and the molecular weight does not increase. As a result, the polymer tend not to be formed into a fiber when spinning is performed.

Further, the polyalkylene glycol has an average molecular weight of preferably 150 to 1,000.

When the polyalkylene glycol has an average molecular weight falling within the above-mentioned range, dyeing can be performed under normal pressure at around 100° C., and a thickening action attributed to a sulfonate group can be reduced because the polyalkylene glycol exerts a plasticizing effect. As a result, the degree of polymerization of the polymer can be increased.

The above-mentioned polyalkylene glycol is represented by the general formula HO(C_(n)H_(2n)O)_(m)H (where n and m each represent a positive integer). A polyethylene glycol where n equals 2 is most preferred because polyethylene glycol is universally used.

The above-mentioned polyester specifically refers to a polyester polymer capable of forming a fiber such as polyethylene terephthalate, polybutylene terephthalate, or polyethylene naphthalate. Further, the polyester may contain titanium oxide.

Further, the copolymerized polyester to be used in the present invention desirably contains diethylene glycol (hereinafter referred to as “DEG”) at 4.5 to 6.0 mol %. DEG is produced by a side reaction during the polymerization. When the content of DEG is less than 4.5 mol %, cationic dyeing performance under normal pressure deteriorates. Further, when the content of DEG exceeds 6.0 mol %, the heat resistance and oxidation resistance of the polymer deteriorate. As a result, operability at a time of melt spinning deteriorates markedly.

In addition, a concentration of terminal carboxyl groups in the polymer is preferably set to 20 to 30 eq/ton. When the concentration of the terminal carboxyl groups is less than 20 eq/ton, coloring of the polymer to be pushed out of a polymerization tank is not good. When the concentration exceeds 30 eq/ton, the heat resistance deteriorates in a spinning process or a post process.

The polyester to be used in the present invention preferably has such a limiting viscosity that a ratio of a maximum value [η]max of the limiting viscosity to a minimum value [η]min of the limiting viscosity satisfies the relationship of 1.0≦[η]max/[η]min≦1.02. When the ratio [η]max/[η]min deviates from the above-mentioned range, operability tends to be inferior. For example, yarn breakage frequently occurs at a time of melt spinning, and the lifetime of a spinneret reduces because of poor spinning filterability.

The conductive layer contains titanium oxide particles each having a conductive coating film. This way, the conjugated conductive fiber is provided with conductive performance, and no static electricity is generated when one wears clothes produced by blending the conjugated conductive fiber with an acrylic fiber.

The conductive coating film is formed of, for example, copper oxide, silver oxide, zinc oxide, cadmium oxide, tin oxide, lead oxide, or manganese oxide.

A second component may be added to the conductive coating film. The second component is, for example, a dissimilar metal oxide or a similar or dissimilar metal. For example, suitable is a component containing copper oxide/copper, zinc oxide/aluminum oxide, tin oxide/antimony oxide, zinc oxide/zinc, aluminum oxide/aluminum, tin oxide/tin, antimony oxide/antimony, or any one of oxides thereof a part of which is reduced.

The titanium oxide particles each having the conductive coating film have a specific resistance of, in a powder state, preferably 10⁴Ω·cm (order) or less, particularly preferably 10²Ω·cm (order) or less.

The specific resistance of the particles described above is measured by: filling 10 g of a sample into a cylinder having a diameter of 1 cm; applying a pressure of 200 kg with a piston from the upper side of the filled sample; and applying a direct current (0.1 to 100 V).

The titanium oxide particles each having the conductive coating film each desirably have as small a particle diameter as possible from the viewpoints of spinnability and conductivity. For example, used are titanium oxide particles having an average particle diameter of preferably 1 μm or less, particularly preferably 0.7 μm or less, most preferably 0.5 to 0.01 μm. As the titanium oxide particles each have a smaller particle diameter, when the particles are mixed with a polymer, the particles are more excellent in dispersibility in the polymer and the resultant mixture is more excellent in conductivity.

The conductive coating film can be formed by, for example, a vacuum deposition method, or a method involving: causing a metal compound (e.g., organic acid salt) to adhere; and sintering the resultant to produce an oxide and partially reducing the oxide as required.

Any known thermoplastic polymer can be used as the polymer which forms the conductive layer by being mixed with the titanium oxide particles having the conductive coating film. For example, one can use polyamide, polyester, polyolefin, and polycarbonate. Any thermoplastic resin is applicable as long as the resin takes on a fiber shape when being subjected to melt spinning. Of those, polyethylene is preferred.

A mixing ratio of the titanium oxide particles having the conductive coating film in the conductive layer is preferably 30 to 85 wt %. The mixing ratio is more preferably 50 to 85 wt %, still more preferably 60 to 85 wt %.

When the mixing ratio of the titanium oxide particles having the conductive coating film falls within the above-mentioned range, conductive performance is good.

In the conjugated conductive fiber of the present invention, the non-conductive layer is requested to account for at least 70% of the surface of the fiber. For example, suitable is a conjugated fiber in which a non-conductive layer A and a conductive layer B each have a cross-sectional shape as illustrated in any one of FIGS. 1 to 4.

In consideration of the uniformity of dyeing, suitable is a fiber in which the non-conductive layer A occupies the entirety of the surface of the fiber as illustrated in any one of FIGS. 1 to 4.

A ratio of the conductive layer B to the non-conductive layer A is preferably 1:30 to 2:1 in terms of an area ratio of the cross-section surface of the fiber. The ratio is more preferably 1:30 to 1:1.

When the ratio of the conductive layer B is more than 2:1, the strength of the fiber decreases, and spinning and winding tend to be impossible. Further, when the ratio of the conductive layer B is less than 1:30, the conductivity of the fiber becomes insufficient, and the fiber tends to become incapable of exhibiting an antistatic effect.

A method of mixing the polymer and the titanium oxide having the conductive coating film, both of which are used in the conductive layer B of the conjugated conductive fiber, is not particularly limited. The mixing is performed by a known method such as biaxial kneading. With the resultant conductive resin, the production of the conjugated conductive fiber is performed by, for example: melting the conductive resin and the polyester for the non-conductive layer A, respectively; and ejecting the melted products from a spinneret so that the products may each have, for example, a cross-sectional shape as illustrated in FIG. 1.

After the ejected conjugated yarn has been cooled with cold air, an oil agent is added thereto, and the yarn is wound with a known winder. Thus, a multifilament or a monofilament is obtained. Any winding speed is applicable as long as the speed is suitable for the combination and ratio of the conductive layer and the non-conductive layer. The speed is desirably 600 m/min to 1,600 m/min in terms of the quality of the yarn, ease with which the yarn is wound, and the like.

The resultant un-drawn yarn is drawn while heat of 80 to 120° C. is applied. Thus, the conjugated conductive fiber is obtained.

The conjugated conductive fiber has an electrical resistance value of preferably 1×10⁷ to 1×10¹¹ Ω/cm.

The drawn yarn has a monofilament fineness of desirably 1.5 to 5.0 dtex when the conjugated conductive fiber is blended with an acrylic fiber.

Next, a method of utilizing the conjugated conductive fiber of the present invention is described. The resultant conjugated conductive fibers are bundled so as to have a fineness of, for example, around 300,000 dtex, thereby providing a tow. The conductive yarns formed into the tow are subjected to crimping by a known method. After the crimping, a spinning oil agent is removed. An after oil is added to the tow and the tow is dried so as to be blended with acrylic fibers. After drying, the tow is cut so as to have a length of 5 mm or less and then formed into a floc. The floc is mixed into an acrylic floc which has been separately produced by an ordinary method at one to several tens of percent by weight. Any mixing ratio is applicable as long as the ratio is suitable for antistatic performance necessary for the final product. After mixing, the resultant is formed into a tow by a known method. The resultant conjugated conductive fiber-mixed acrylic tow is further combined with a non-conductive acrylic tow to further form a tow. The tow is wound in a cheese shape as a spun yarn.

For cheese dyeing, the resultant cheese of the acrylic yarns is dyed with a cationic dye at 98° C. for 45 minutes to 60 minutes. The dyed conjugated conductive fiber-mixed acrylic yarns are knitted by a known method and then subjected to a raising treatment, thereby producing clothes such as fleeces.

The conjugated conductive fiber of the present invention is innovative because the fiber can be dyed under the same conditions as those for an acrylic fiber and does not appear as spots, and clothes made of acrylic fibers each blended with the conjugated conductive fibers of the present invention can suppress the generation of static electricity as well.

EXAMPLES

Hereinafter, the present invention is specifically described by way of examples. However, the present invention is not limited thereto. It should be noted that each evaluation was performed as described below.

(1) Antistatic Property

A wearing test was performed with respect to the antistatic property by producing clothes in which the product of the present invention was blended with acrylic fibers. The case where the generation of static electricity, with crackling when one takes off the clothes after wearing, was not observed was reported as ◯. The case where the generation of the static electricity was observed was reported as x.

(2) Dyeability

Evaluation for dyeability was performed by: dyeing a product obtained by blending the product of the present invention with acrylic fibers under normal pressure with 2% omf of a Kyacryl Red GL and 0.2 cc/l of acetic acid at a bath ratio of 1:50; and visually evaluating the result. The case where spots of the conjugated conductive yarn were not observed was reported as ◯. The case where spots were observed was reported as x.

(3) Electrical Resistance Value

An electrical resistance value was measured by: cutting the conjugated conductive yarn so that the resultant sample had a length of 10 cm; applying a conductive paste (Product name: DOTAITO) to both of the ends of the sample; then clipping both of the ends of the sample with square-shaped aluminum foils about 1 cm on a side; and clipping the aluminum foils with alligator clips of an resistance measuring apparatus (measuring apparatus: AG4339B, manufactured by Agilent Technologies, Inc., measuring environment: 23° C.×60% RH).

Inventive Example 1

Used as the conductive layer was a polymer obtained by allowing polyethylene to contain 75 wt % of titanium oxide particles coated with tin oxide doped with antimony oxide. Used as the non-conductive layer was a polyester capable of forming a fiber, the polyester containing 2.5 mol % of the SIPE with respect to an acid component of the polyester and 5.0 wt % of a polyethylene glycol having an average molecular weight of 200 with respect to the polyester. It should be noted that, in the polyester capable of forming a fiber in the non-conductive layer, a content of diethylene glycol with respect to a glycol component was 5.9 mol %, a concentration of terminal carboxyl groups was 25 eq/ton, and a limiting viscosity ratio [η]max/[η]min was 1.005.

In order to provide each of the above-mentioned conductive layer and non-conductive layer with a cross-section surface as illustrated in FIG. 1, the layers were ejected while spinning from an orifice having a temperature of 275° C. and a diameter of 0.25 mm, subjected to cooling and oiling, wound at a speed of 1,200 m/min, and drawn while applying heat of 100° C. As a result, a drawn yarn having a fineness of 80 dtex/24f was obtained.

The resultant drawn yarn had a strength of 2.9 cN/dtex, an elongation of 40%, and an electrical resistance of 5.74×10⁸ Ω/cm.

Next, each resultant drawn yarns were formed into a short-fiber floc as described above in detail. 10 weight percent of the floc was contained in an acrylic floc, thereby providing a tow. The resultant tow was combined with 19 non-conductive acrylic tows so as to have a total content of 0.5 wt %. Thus, a spun yarn was obtained. A cheese winding of the spun yarns was dyed with 2% omf of a Kyacryl Red GL and 0.2 cc/l of acetic acid at a bath ratio of 1:50 and 98° C.×60 minutes. After that, the resultant was knitted and then subjected to a raising treatment. Thus, a fleece was produced.

In the resultant fleece, no dyeing spots were observed, and the generation of static electricity in the wearing test was not observed either.

Although specific forms of embodiments of the instant invention have been described above and illustrated in the accompanying drawings in order to be more clearly understood, the above description is made by way of example and not as a limitation to the scope of the instant invention. It is contemplated that various modifications apparent to one of ordinary skill in the art could be made without departing from the scope of the invention.

The conjugated conductive fiber of the present invention is a conjugated conductive fiber which: can be dyed under normal pressure; has good color developing property; and can reduce the generation of static electricity. The conjugated conductive fiber is suitably blended with an acrylic fiber. 

1. A conjugated conductive fiber, comprising a non-conductive layer and a conductive layer, wherein: the non-conductive layer accounts for at least 70% of a surface of the fiber; the non-conductive layer comprises a polyester obtained by copolymerizing a metal sulfonate group-containing isophthalic acid and a polyalkylene glycol; and the conductive layer comprises a thermoplastic polymer containing titanium oxide particles each having a conductive coating film.
 2. The conjugated conductive fiber according to claim 1, wherein a mixing ratio of the titanium oxide particles each having the conductive coating film in the conductive layer is 30 to 85 wt %.
 3. The conjugated conductive fiber according to claim 1, wherein a ratio of the conductive layer to the non-conductive layer is 1:30 to 2:1 in terms of an area ratio of a cross-section surface of the fiber. 